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STM32F439NIH can't get PLLCLK on MCO1 (solved)

Question asked by Hoei.Lasse on Feb 17, 2017
Latest reply on Feb 17, 2017 by Hoei.Lasse

I want to have 60 MHz on the MCO1 pin PA8. I use an external 25 Mhz crystal. The PLL delivers 180 Mhz to the system clock. I've used STCubeMX to configure the clocks to get 180 MHz / 3 on MCO1.


Unfortunatly I'm not getting any activity on the MCO1 pin at all.


Some things I've tried:

- Checking the registers in the debugger, looks correct.

- Setting MCO1 register to 0x02 for using HSE. This works fine, I'm getting pulses on MCO1

- Setting PLL down to 75 Mhz. No activity on MCO1.


Is this some limitation or erratta that I somehow missed in the documentation?